a. Field of the Invention
This invention relates to a method and an apparatus for color conversion when a color of an image original is to be converted into another color. More particularly, the present invention is concerned with a color reproduction apparatus incorporating therein the above mentioned color-conversion apparatus.
b. Description of the Prior Art
Usually, in the color reproduction apparatus adopting the electrophotographic method, color reproduction has been obtained by a combination of a several kinds of color-separation filters for separating colors in the image original and a developing agent, or developer, containing therein several kinds of coloring pigments. For instance, blue, green, and red filters are used as the color-separation filters, and pigments in yellow (hereinafter abbreviated as "Y"), magenta (hereinafter abbreviated as "M"), and cyan (hereinafter abbreviated as "C") colors are used as the developer. For obtaining a reproduced copy of an image original as it is, it has been a usual practice to follow the following process steps in the color reproduction apparatus as shown in FIG. 1.
Step 1: Using a blue filter BF in the filter 4, a color original is subjected to color-separation and then exposed on a photosensitive layer 8, thereby forming a latent image containing Y and a color containing therein Y (i.e., red and green). This color latent image is developed in a Y developing device 17, and the developed image is transferred onto paper 16.
Step 2: Using a green filter GF, the color original is subjected to color-separation and exposure to obtain a latent image in M and a color containing M (i.e., red and blue). This color latent image is developed in an M developing device 18, and the developed image is transferred onto paper 16.
Step 3: Using a red filter RF, the color original is subjected to color-separation and exposure to obtain a latent image in C and a color containing C (green and blue). This color latent image is developed in a C developing device 19, and the developed image is transferred onto paper 16.
In the above-described process steps, images in colors Y, M, and C are sequantially transferred onto the reproduction paper, and the final image copy is obtained by heat-fixing the transferred image by a heat-fixing device 11.
Thus, the color copy has been obtained with faithful reproducibility of the color original through three process steps by determining a combination of the color-separation filter and the developing agent.
While it is readily conceivable that reproduction of different color from that of the color original by changing combination of the developer, or changing the number of process steps from three to any arbitrary number, it is really a complicated work to determine proper combination between the color-separation filter and the developer on the basis of the relationship between the color original and the color to be reproduced.
Also, in order to reproduce the image original in a mono-color or bi-color by the use of the abovementioned steps for faithfully reproducing the image original, a long span of time is required for completion of the process. In this case, even if the combination of the developing device and the filter is made manually selectable, it is still not known whether the reproduced copy to be obtained is faithful to the original image color, or not, or which color in the image original changes, and how. In this consequence, more time is taken for the reproduction process which should be carried out while comparing with a color chart.